The present invention relates generally to heating, ventilation and air conditioning (HVAC) systems and thermal systems for rechargeable energy storage systems (RESS), such as battery packs, in vehicles.
Advanced automotive vehicles are being introduced that employ an RESS, such as a battery pack or other rechargeable energy storage means, to store large amounts of energy for electric propulsion systems. These vehicles may include, for example, plug-in hybrid electric vehicles, electric vehicles with an internal combustion engine that is used as a generator for battery charging, and fuel cell vehicles. In general, the RESS require some type of thermal system, and in particular for cooling and warming a battery pack in order to maximize the charging capacity and life of the battery pack.
Typical battery thermal systems used to cool and warm the battery pack rely on air flow from the vehicle HVAC system. This may be passenger cabin air that is directed through the battery pack. But these systems suffer from drawbacks such as low heat rejection due to the low heat transfer coefficient of air, interior passenger cabin noise, vibration and harshness (NVH) due to battery blower motor and air rush noise, limited battery cooling capacity after the vehicle has been parked in the sun (due to high air temperatures in the passenger cabin at the beginning of the drive cycle), and difficulty in ensuring that an air inlet grille between the passenger cabin and the battery thermal system does not get accidentally blocked by vehicle passengers (resulting in reduced or no battery air cooling flow). Others may employ a separate, dedicated battery pack coolant heater for warming a coolant before it is circulated through the battery pack. However, such separate systems tend to add to the cost, weight and complexity of the overall vehicle heating and cooling systems.